has become snow; the particles are elongated, and by pointing to the
charged rod indicate the lines of electrostatic force very
beautifully; electrify further, and the air is perfectly clear. Next
burn turpentine, and electrify gently; the dense black smoke
coagulates into black masses over an inch long; electrify further, and
the glass is covered with soot, but the air is clear. Turpentine smoke
acts very well, and can be tried on a larger scale; a room filled with
turpentine smoke, so dense that a gas-light is invisible inside it,
begins to clear in a minute or two after the machine begins to turn,
and in a quarter of an hour one can go in and find the walls thickly
covered with stringy blacks, notably on the gas-pipes and everything
most easily charged by induction. Next fill a bell-jar full of steam,
and electrify, paying attention to insulation of the supply point in
this case. In a few seconds the air looks clear, and turning on a beam
of light we see the globules of water dancing about, no longer fine
and impalpable, but separately visible and rapidly falling. Finally,
make a London fog by burning turpentine and sulphur, adding a little
sulphuric acid, either directly as vapor or indirectly by a trace of
nitric oxide, and then blowing in steam. Electrify, and it soon
becomes clear, although it lakes a little longer than before; and on
removing the bell-jar we find that even the smell of SO2 has
disappeared, and only a little vapor of turpentine remains. Similarly
we can make a Widnes fog by sulphureted hydrogen, chlorine, sulphuric
acid, and a little steam. Probably the steam assists the clearing when
gases have to be dealt with. It may be possible to clear the air of
tunnels by simply discharging electricity into the air--the
electricity being supplied by Holtz machines, driven say by small
turbines--a very handy form of power, difficult to get out of order.
Or possibly some hydro-electric arrangement might be devised for the
locomotive steam to do the work. I even hope to make some impression